1. Field of the Invention
The present invention relates to a light guide plate, and more particularly to a light guide plate for a backlight system used in a liquid crystal display.
2. Description of the Related Art
For the sake of comparison, a conventional backlight system of a liquid crystal display will be previously described in the following with reference to FIGS. 1 to 3.
Referring to FIG. 1, a conventional backlight system of a liquid crystal display includes a lamp 11, a light guide plate 12, a lamp reflector 13, and a back reflector 14.
The lamp 11 is used as a light source to provide the backlight system with the necessary light beams.
The light guide plate 12 has a front surface 121, a back surface 122, and a side surface 123 that is adjacent to the lamp 11. In addition, the side surface 123 is disposed to be parallel with the lamp 11 so as to receive the light beams irradiated by the lamp 11. The back surface 122 is provided with a plurality of reflector dots 124, each of which is designed as a hemispherical protrusion.
The lamp reflector 13 is disposed to surround the lamp 11 in such a way that the light beams irradiated by the lamp 11 is reflected toward the light guide plate 12.
The back reflector 14 is disposed on the back surface 122 of the light guide plate 12 to thereby reflect back the light beams transmitting out of the back surface 122 of the light guide light 12.
As shown in FIG. 1, in normal situations, a light beam B irradiated from the lamp 11 through the side surface 123 into the light guide plate 12 is totally reflected back and forth between the front surface 121 and the back surface 122 in such a way of propagating away from the lamp 11. In this case, there are no light beams refracted out of the front surface 121 of the light guide plate 12. However, if a light beam A irradiated from the lamp 11 hits against any of the reflection dots 124 during propagating, a reflective light beam A1 refracts out of the front surface 121 as a result of a change of the reflective angle of the light beam A. With the disposition of the reflector dots described above, the backlight necessary for a panel 17 of the liquid crystal display is thereby provided.
As a conventional method for fabricating the reflector dots 124 of the light guide plate 12, a halftone printing process is used to print a high reflective material over the back surface 122 of the light guide plate 12, thereby forming the reflector dots 124. Undesirably, the manufacturing of the back light system used in the liquid crystal display takes a long time and costs expensively due to the requirement of the halftone printing process.
As another conventional method for fabricating the reflector dots 124 of the light guide plate 12, a plurality of reflector dots 124 are directly fabricated as an integral part of the light guide plate 12 on the back surface 122. For example, each of the reflector dots 124 may be shaped like a hemisphere, a trapezoid, a pyramid, or a half-moon. However, the trapezoid and half-moon reflector dots only reflect out of the front surface 121 the incident light beams propagating in a certain direction. Therefore, these reflector dots are not applicable to a condition that the incident light beams propagate in a number of directions. Although the hemispherical reflector dots are applicable to a condition that the incident light beams propagate in a number of directions, their ability to reflect and refract the light beams out of the light guide plate is still not optimum as described below.
Referring to FIGS. 2(a) and 2(b), each reflector dot 124 is designed as a hemispherical protrusion. Since each reflector dot 124 is no more than a single protrusion as observed in any directions, there is only a local reflection region capable of effectively reflecting and refracting the incident light beam out of the light guide plate. For example, only a local reflection region 126 is able to effectively reflect and refract out of the light guide plate the incident light beam propagating in the X direction. This is because only the local reflection region 126 can effectively change the reflective angle of the incident light beam propagating in the X direction.
Referring to FIG. 3, which is a three-dimensional view, when the light beam A hits against the reflection dot 124, only part of the light beam A is reflected as a reflective light beam A1 which is then refracted out of the front surface 121 of the light guide plate. Therefore, the reflecting efficiency of the conventional light guide plate still needs an improvement.
An object of the present invention is to provide a light guide plate for a backlight system, which is applicable to a condition that the incident light beams propagate in a number of directions and is able to effectively reflect and refract the incident light beams out of the front surface of the light guide plate.
In order to achieve the object described above, a light guide plate for a backlight system according to the present invention is disclosed. The backlight system consists of a light guide plate, a lamp, a lamp reflector, and a back reflector. The lamp reflector is disposed to surround the lamp for reflecting the light beams irradiated by the lamp toward the light guide plate. The light guide plate has a front surface facing a panel; four end surfaces, one of which is disposed to face the lamp; and a back surface on which the back reflector is disposed. The back surface of the light guide plate is integrally formed with a plurality of reflector units. Each of the plurality of the reflector units includes at least an annular protrusion.
With the disposition of the plurality of reflector units described above, the light guide plate effectively reflects the incident light beams into at least two reflective light beams which are then refracted out of the front surface even if the incident light beams propagate in a number of directions. Therefore, the light guide plate according to the present invention achieves an excellent reflective efficiency.